1. Field of the Invention
The present application is directed to a run-flat device that is inserted into a tire, and, more specifically, to non-pneumatic run flat device.
2. Description of the Related Art
Run-flat devices allow continued use of a vehicle riding on pneumatic tires in the event that the pneumatic tires are damaged and unable to carry the required load. There are many types of run-flat devices. Most run-flat devices comprise a solid elastomer or rigid metal design that is positioned within an outer shell of the pneumatic tire. Solid elastomer run-flat tires are difficult to install due to their one-piece design and the rigidity of the bead steel in pneumatic tires. Such run-flat devices are also heavy due to their solid design. These run-flat devices therefore add rotating and static mass to the entire wheel assembly. The solid run-flat devices also provide little cushion, resulting in a rough ride, which can damage the vehicle.
Rigid metal designs are typically easier to assemble since they can be made in several pieces but have even less cushion as compared to solid elastomer designs. The increased stiffness with rigid metal designs can also cause problems when the inflated tire is subjected to impact loads or obstacles at speed. In addition, if the run-flat device with a rigid metal design is deformed enough to reach the run-flat, the sudden impact can subject the suspension and vehicle to unacceptable accelerations.
Another type of run-flat tire device relies on providing the tire with a thick sidewall that provides structural support when the tire loses air pressure. However, the thick sidewall results in a harsher ride during normal, pneumatic operation. Such thick sidewall tires also have a limited lifetime after puncture due to the heat generated by the flexing of the sidewall during operations. The event that caused the tire to lose pressure can also affect the structural integrity of the side wall.